The summer-blooming annual forbs Cleome lutea and Cleome
serrulata (Cleomaceae) are native across the US Intermountain
West and Rocky Mountains, respectively. Their farmed seed is
sought to help rehabilitate western rangelands in those regions.
This study of the reproductive biologies and pollinator faunas
of C. lutea and C. serrulata is the first for this
cosmopolitan family, the sister family to the Brassicaceae. Unlike
the S-allele self-incompatibility systems of some Brassicaceae,
both species of Cleome were found to be self-fertile and capable
of some autogamy. Compared with selfing, outcrossing did not
enhance seed set, seed viability or seedling vigor for either
species (in fact, selfed progeny were more robust). Large, openly
visited plants yielded >20 000 seeds each. Like several species
of the sister family Capparaceae, flowers of both species first
shed their pollen, secreted nectar and became receptive nocturnally.
Although no nocturnal visitors were found, both Cleome species
attracted a diverse array of diurnal native bees, wasps and butterflies.
Among the many floral generalist bees that work Cleome flowers
for pollen and nectar are two managed agricultural pollinators,
Apis mellifera and Megachile rotundata. These observations
bode well for pollinating C. lutea and C. serrulata
in small commercial seed fields. It appears that diverse wild
bees would benefit from the addition of native Cleome to restoration
seed mixes, with the objective of sustaining native pollinator
faunas during the first few years of postfire plant community
rehabilitation.